Right, a lay system for the new year.
In races where the fav is odds on (TAB prices), lay any horse under $10 on the TAB, who placed 1-3 at its last start.

Results from 1/1/09 to April 2010

Selections: 2549
Return: 1668.80 (-880.20)
POT: -34.5%

Even allowing for the higher BF prices, you should be able to make this work.

Does that include resumers?

Would you also lay the odds-on shot if it qualifies.

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Cheers.

Includes resumers.
Sorry should have made it clear, dont lay the odds on pop.

Ran this on my db.
The problem is a $10 chance on the tote could be $20+ on betfair.

It showed a negative expectation. The betfair odds in my db showed a difference of tote to betfair prices of 46% on these selections.

Taking your figures and applying the 46% differences I got :

Selections: 2549
Return: 1668.80 *1.46 = $2436
POT: -5%

After applying the 5% commission = break even or close enough.

Of course depends on the prices obtained. I am just doing some simple analysis here to give a quick indication of profitability.

My calculations show you will be laying on average a -0.95% expectation and any negative expecation is not a good thing. Expectation is worked out on strike rate and avg lay odds.